Kartika et al. Int. Sem. Chem. Eng. Soehadi Reksowardojo 2011
ISBN 978-979-98300-1-2
Jatropha curcas oil is regarded as a potential diesel substitute. Vegetable oils used as alternative fuel have numerous advantages. They are notably non toxic, safely stored and
handled because of their high flash point. The fact that jatropha oil cannot be used for nutritional purposes without detoxification makes its use as an energy source for fuel
production very attractive.
The preparation of biodiesel from various vegetable oils based on alkaline transesterification of triglycerides with polyhydric alcohol has been studied for several
decades, and a major amount of industrial production has been achieved with this method [6,7]. However, the transformation of jatropha seed in oil industry requires extra-steps
during the extraction and refining processes. As the cost of the vegetable oil production contributes to approximately 70 of the biodiesel production cost [8,9], there is a need
for the development of a new biodiesel production process that is simple, compact, efficient, low-cost, and that consumes less energy.
On the other hand, the preparation of biodiesel based on in situ transesterification has been successfully carried out from various oilseeds [8-15]. In situ transesterification is a
biodiesel production method that uses the original agricultural products as the source of triglycerides instead of purified oil for direct transesterification, and it works virtually
with any lipid-bearing material. It can reduce the long production system associated with pre-extracted oil, and it maximizes ester yield.
The objective of this study was to investigate the in situ transesterification allowing to produce directly biodiesel from jatropha seed. The influences of amount of KOH catalyst,
methanol to seed ratio, amount of n-hexane to methanol and seed ratio, stirring speed, temperature and reaction time were examined to define the best performance of biodiesel
production yield and biodiesel quality.
2 Materials and methods
2.1 Materials
All trials were carried out using jatropha seed that was supplied by Indonesian Spices and Industrial Crops Research Institute Sukabumi, Indonesia. The jatropha seed variety was
the Lampung one. The oil content of the seed, expressed in relation to its dry matter content standard NF V 03-908 was 39.4, or 36.9 in relation to its wet basis. The
seed moisture content at storage was 6.2 standard NF V 03-903. Methanol 98 purity and n-hexane 98 purity were supplied by BRATACO Chemical Ltd
Indonesia. All solvents and chemicals for analysis were pure analytical grades that were obtained from Sigma-Aldrich, Fluka and J.T. Baker Indonesia and France.
2.2 Experimental
In all trials, the moisture content and mesh size of jatropha seed were less than 1 and 35, respectively. To obtain a moisture content of less than 1, the jatropha seed was
dried at 60-70°C during 24-48 h. The dried jatropha seed was then milled using an electric grinder fitted with a mesh size of 35.
For the study of KOH amount effect and methanol to seed ratio effect on biodiesel production yield and biodiesel quality, 100 g of milled jatropha seed were mixed with
methanol in which KOH was firstly dissolved. The amount of KOH and the methanol to
Transformation of Jatropha Seed to Biodiesel by In Situ Transesterification
ISBN 978-979-98300-1-2
seed ratio vw were 0.05-0.1 molL in methanol and 2:1-6:1, respectively. The KOH amount used in this study was based on literature reported elsewhere [13]. 100 ml of n-
hexane [seed to n-hexane ratio wv of 1:1] was then added to increase oil miscibility in the mixture, to accelerate the reaction and to perform it in a single phase. The reaction
was carried out in a three-necked 2000 mL round bottom flask equipped with a reflux system, a magnetic stirrer and a heater, under reaction conditions of 700 rpm for the
stirring speed, 60°C for the temperature and 4 h for the reaction time.
Upon achieving reaction period, the mixture was cooled to room temperature, and was vacuum filtered to separate the filtrate from a cake. The filtrate was then evaporated using
a rotary evaporator to recover methanol and n-hexane, and allowed to settle to be separated into two layers. The lower layer was dark brown in color and contained
glycerol, while the upper layer was yellow in color and contained the fatty acid methyl esters crude biodiesel and the unreacted triglycerides. The upper layer was then washed
with water until neutrality, and dried at 105°C during 1 h. The mass of upper layer was measured, and the biodiesel production yield was calculated using the formula:
Mass of biodiesel after washing and drying g Biodiesel yield =
——————————————————— × 100 Mass of oil contained in jatropha seeds g
The cake was dried overnight at room temperature. The total volatile matter content standard NF V 03-903 and the n-hexane extracted matter content standard NF V 03-
908 were the determined.
For the study of the operating conditions effects on biodiesel production yield and biodiesel quality, the experiments were conducted using KOH amount of 0.075 molL in
methanol. The different operating conditions were examined by varying the amount of n- hexane to methanol and seed ratio 1:5:1, 2:4:1, 3:3:1, the stirring speed 200-600 rpm,
the temperature 40-50°C and the reaction time 4-6 h. Sample collection and analysis were performed according to procedure developed in the previous study. The randomized
factorial experimental design with 2 replications and ANOVA F-test at
= 0.05 were applied to study the effects of amount of n-hexane to methanol and seed ratio, stirring
speed, temperature and reaction time on biodiesel production yield and biodiesel quality using SAS software.
2.3 Biodiesel quality analysis
